With this Tweak you will prevent  account changes in Outlook Express.

To do this, follow the next steps:

1. Open the Registry Editor click on the Start button on your taskbar, then click on Run and type "regedit" and click on OK to start the regedit utility.
    
2. Expand HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Outlook Express (see picture 1).
   
   

   Picture 1

3. Create new DWORD value called "No Modify Accts" and set it to "1" to enable the restriction or "0" to allow users to modify accounts.
    
4. The modifications you made will be in effect after you restart Outlook Express.